An air-filled capacitor carries enough charge to store $6.00 \mathrm {~mJ}$ of potential energy. It is then accidentally filled with water in such a way as not to discharge its plates. How much energy does it continue to store after it is filled? The dielectric constant for water is 78 and for air it is $1.0006$.

Question

Quizplus · Accepted Answer

The energy stored in a capacitor is inversely proportional to the dielectric constant. When filled with water, the energy is reduced by a factor of the dielectric constant of water, which is 78. Thus, the new energy is $6.00 \mathrm{~mJ} / 78 \approx 0.077 \mathrm{~mJ}$.

An Air-Filled Capacitor Carries Enough Charge to Store 6.00 mJ6.00 \mathrm {~mJ}6.00 mJ

An Air-Filled Capacitor Carries Enough Charge to Store $6.00 \mathrm {~mJ}$